Ballistic grilles are used to provide protection as well as airflow. Openings for air flow through the grille inherently create protection problems for the occupants of the vehicle. In order to provide protection, the grille must be made of materials to withstand threats so that projectiles do not enter the vehicle. This makes grilles comparatively heavier but not as well protected as the rest of vehicles armor. Bars or louvers of existing grilles may slow or catch a threat, but because they are open they may not fully stop a penetrator, spall or small fragments that may break off and pass thru the openings to impact crew or components behind the grille.
In the prior art, aluminum S-shaped louvers formed grilles, which were used to provide protection for intake and exhaust vents on armored vehicles. Grille armor has consisted of louvers, typically in a chevron or S shape. Made of aluminum or steel, the louvers are spaced to provide a circuitous open path that air can flow through. Projectiles that fly in a straight line are stopped by contact with the louvers. However, thick louvers block airflow or create stagnation points which affect engine performance.
Current grilles by themselves do not provide sufficient protection against high velocity artillery threats. But spacing or pitch of the existing grill leaves sections of the grille fairly open, so that threats don't hit much of the grille. Thus, there is a tradeoff between the desired protection and desired air flow.
Recently development has focused on an existing grille which uses 3″ high×0.25″ thick 4130 steel louvers. The bars are bent at 60 degrees and spaced 1″ apart. When baseline ballistic test and flow models were done it was determined that the grille itself may not be sufficient.
The earlier designs have not worked to maximize the airflow while maintaining protection. A grille design is needed that allows airflow with minimal pressure drops. Air flow is affected by spacing between the bars, width of the bars, and dimensions along the width of the bars. The objective is to create a new grille which improves ballistic protection, reduces pressure drop and maintains flow volume over existing steel bent bar grille.